The molecular biology of anopheline mosquitoes is being studied in relation to the capacity of these vectors to transmit malaria. Systems for cloning and transposing genes into mosquito germ lines are being developed. Factors which render mosquitoes refractory to malarial infection, with special emphasis on mechanisms which encapsulate developing parasites, are being defined. Linkage of refractory genes to genes regulating blood-meal associated physiological events, e.g., vitellogenin synthesis, will be used to enhance refractory responses. Additional parasiticidal mechanisms from within and outside of mosquitoes are being sought with special emphasis on the evaluation of magainins, cecropins and defensins, their physiological effects on in vivo parasite development and the molecular biology of the genes coding for their production. The ability to identify, clone and transpose genes which regulate mechanisms should permit the development of mosquito lines incapable of transmitting malaria for use in malaria control schemes.